diff --git a/biojava-structure/src/main/java/org/biojava/nbio/structure/io/cif/CifStructureConsumerImpl.java b/biojava-structure/src/main/java/org/biojava/nbio/structure/io/cif/CifStructureConsumerImpl.java
index fb3214be96..9393e285c3 100644
--- a/biojava-structure/src/main/java/org/biojava/nbio/structure/io/cif/CifStructureConsumerImpl.java
+++ b/biojava-structure/src/main/java/org/biojava/nbio/structure/io/cif/CifStructureConsumerImpl.java
@@ -217,7 +217,8 @@ public void consumeAtomSite(AtomSite atomSite) {
                 isHetAtmInFile = true;
             }
 
-            String insCodeString = pdbxPDBInsCode.get(atomIndex);
+            String insCodeString = pdbxPDBInsCode.isDefined()? pdbxPDBInsCode.get(atomIndex) : null;
+
             Character insCode = null;
             if (insCodeString != null && !insCodeString.isEmpty() && !"?".equals(insCodeString)) {
                 insCode = insCodeString.charAt(0);
@@ -246,7 +247,8 @@ public void consumeAtomSite(AtomSite atomSite) {
             }
 
             String asymId = labelAsymId.get(atomIndex);
-            String authId = authAsymId.get(atomIndex);
+            String authId = authAsymId.isDefined()? authAsymId.get(atomIndex) : asymId;
+
             if (currentChain == null) {
                 currentChain = new ChainImpl();
                 currentChain.setName(authId);
@@ -277,7 +279,9 @@ public void consumeAtomSite(AtomSite atomSite) {
                 }
             }
 
-            ResidueNumber residueNumber = new ResidueNumber(authId, authSeqId.get(atomIndex), insCode);
+            int authSeqIdInt = authSeqId.isDefined()? authSeqId.get(atomIndex) : (int)seqId;
+
+            ResidueNumber residueNumber = new ResidueNumber(authId, authSeqIdInt, insCode);
 
             String recordName = groupPDB.get(atomIndex);
             String compId = labelCompId.get(atomIndex);
@@ -289,7 +293,7 @@ public void consumeAtomSite(AtomSite atomSite) {
             }
 
             Group altGroup = null;
-            String altLocation = labelAltId.get(atomIndex);
+            String altLocation = labelAltId.isDefined()? labelAltId.get(atomIndex) : null;
 
             if (startOfNewChain) {
                 currentGroup = createGroup(recordName, oneLetterCode, compId, seqId);
diff --git a/biojava-structure/src/test/java/org/biojava/nbio/structure/io/cif/CifFileConsumerImplTest.java b/biojava-structure/src/test/java/org/biojava/nbio/structure/io/cif/CifFileConsumerImplTest.java
index 0d2ddaf4f6..a8925afa88 100644
--- a/biojava-structure/src/test/java/org/biojava/nbio/structure/io/cif/CifFileConsumerImplTest.java
+++ b/biojava-structure/src/test/java/org/biojava/nbio/structure/io/cif/CifFileConsumerImplTest.java
@@ -181,7 +181,7 @@ private static int[] countEntityTypes(List<EntityInfo> entities) {
 
     /**
      * This tests for cases where dots appear in integer fields. Unusual but it happens in some PDB entries like 1s32.
-     * See issue https://github.com/biojava/biojava/issues/368
+     * See issue <a href="https://github.com/biojava/biojava/issues/368">...</a>
      */
     @Test
     public void specialCases() throws IOException {
@@ -220,4 +220,51 @@ public void specialCases() throws IOException {
         column.valueKinds().forEach(vk -> assertEquals(ValueKind.NOT_PRESENT, vk));
         column.stringData().forEach(sd -> assertTrue(sd.isEmpty()));
     }
+
+    /**
+     * Testing files with atom_site that doesn't have author fields. E.g. cif files from Meta's ESM Atlas (<a href="https://esmatlas.com">...</a>)
+     */
+    @Test
+    public void testAtomSiteWithMissingAuthFields() throws IOException {
+        // taken from MGYP000911143359.cif
+        String mmcifStr =
+                "data_\n" +
+                        "loop_\n" +
+                        "_atom_site.group_PDB\n" +
+                        "_atom_site.id\n" +
+                        "_atom_site.type_symbol\n" +
+                        "_atom_site.label_atom_id\n" +
+                        "_atom_site.label_comp_id\n" +
+                        "_atom_site.label_asym_id\n" +
+                        "_atom_site.label_entity_id\n" +
+                        "_atom_site.label_seq_id\n" +
+                        "_atom_site.Cartn_x\n" +
+                        "_atom_site.Cartn_y\n" +
+                        "_atom_site.Cartn_z\n" +
+                        "_atom_site.occupancy\n" +
+                        "_atom_site.B_iso_or_equiv\n" +
+                        "_atom_site.pdbx_PDB_model_num\n" +
+                        "\n" +
+                        "ATOM 1 N N MET A 1 1 -26.091 68.903 7.841 1.00 90.0 1\n" +
+                        "ATOM 2 C CA MET A 1 1 -26.275 67.677 7.069 1.00 91.0 1\n" +
+                        "ATOM 3 C C MET A 1 1 -24.933 67.025 6.755 1.00 90.0 1\n" +
+                        "ATOM 4 C CB MET A 1 1 -27.033 67.967 5.773 1.00 89.0 1\n" +
+                        "ATOM 5 O O MET A 1 1 -24.314 67.331 5.734 1.00 90.0 1\n" +
+                        "ATOM 6 C CG MET A 1 1 -28.544 67.973 5.934 1.00 86.0 1\n" +
+                        "ATOM 7 S SD MET A 1 1 -29.390 68.904 4.598 1.00 86.0 1\n" +
+                        "ATOM 8 C CE MET A 1 1 -29.202 67.734 3.224 1.00 83.0 1\n" +
+                        "ATOM 9 N N ASN A 1 2 -24.267 66.233 7.730 1.00 90.0 1\n" +
+                        "ATOM 10 C CA ASN A 1 2 -22.897 65.827 8.029 1.00 91.0 1\n" +
+                        "ATOM 11 C C ASN A 1 2 -22.600 64.427 7.500 1.00 90.0 1\n" +
+                        "ATOM 12 C CB ASN A 1 2 -22.634 65.893 9.535 1.00 88.0 1\n" +
+                        "ATOM 13 O O ASN A 1 2 -23.092 63.436 8.044 1.00 89.0 1\n" +
+                        "ATOM 14 C CG ASN A 1 2 -22.191 67.269 9.990 1.00 86.0 1\n" +
+                        "ATOM 15 N ND2 ASN A 1 2 -22.255 67.511 11.294 1.00 87.0 1\n" +
+                        "ATOM 16 O OD1 ASN A 1 2 -21.795 68.108 9.177 1.00 87.0 1\n" ;
+        MmCifFile cifFile = CifIO.readFromInputStream(new ByteArrayInputStream(mmcifStr.getBytes())).as(StandardSchemata.MMCIF);
+        Structure s = CifStructureConverter.fromCifFile(cifFile);
+        assertNotNull(s);
+        assertEquals(2, s.getPolyChain("A").getAtomGroups().size());
+        assertEquals(2, s.getPolyChainByPDB("A").getAtomGroups().size());
+    }
 }
\ No newline at end of file